1. Field of the Invention
The present invention is directed towards and new and improved, linear flow, turn down valve for metering gaseous fuels such as LP gases and natural gas. More particularly, the linear flow turn down valve is especially designed for use with gaseous fuel burners and provides for a maximum flow when the valve is initially turned on and thereafter a substantially linearly decreasing gas flow rate is provided as the valve control shaft is rotated toward a low or minimum flow value which is adjustable for particular applications. The linear flow turn down metering valve, in accordance with the present invention, is also especially adapted for use with both LP gases and natural gases and is designed to provide a substantially or approximately straight line or linear relationship between the gas flow rate and a rotative knob position to afford a user precise and repeatable control of the amount of heat generated at a gaseous fuel burner downstream of the valve.
2. Description of the Prior Art
Commercially viable existing gas valves used for gas ranges and the like generally provide an off/on function along with discrete low, medium and high flow settings. These types of valves generally do not provide for infinitely variable control of gas flow and also many of these valves do not have an adjustable low flow or minimum flow value suitable for simmering and other low heat value applications commonly utilized and needed.
U.S. Pat. No. 2,526,017 discloses a gas valve which when moved from a closed to an open position, opens rapidly and then closes slowly to regulate the flow of fuel. U.S. Pat. No. 2,626,160 discloses a gas valve having a mechanism whereby a selection for relatively large number of flame types of varying size and intensity can be made. U.S. Pat. No. 2,650,610 discloses a gas valve which may be turned from the off position directly to an on position and then turned gradually to decrease the flow through an infinite number of positions to a simmer position. U.S. Pat. No. 2,650,612 discloses a gas valve having a plug with a plurality or series of ports yet still provides infinitely variable flow control rates. U.S. Pat. No. 2,650,613 and 2,650,614 disclose graduated universal valves for gas appliances having a slitted sleeve and an interconnected sleeve, respectively.
U.S. Pat. No. 2,893,426 discloses a universal gas valve that has improved accuracy and adjustability and employs an arcuate radial slot in a conically-shaped valve plug for throttling gas from an input port to an axial outlet port. U.S. Pat. No. 3,001,547 discloses a universal gas valve of a similar type characterized by the metering effect of a tapered port which is opened or closed to the flow position by the longitudinal movement of a sleeve. U.S. Pat. No. 3,273,595 discloses a gas flow control valve providing an improved click-stop, indexed type multiple position burner control and U.S. Pat. No. 3,727,882 discloses a metering valve having a valve plug with an annular groove tapering from zero width to full width and in communication with a port and a rotatable valve seat member.
U.S. Pat. Nos. 4,779,643 and 4,862,917 disclose complex and relatively complicated fuel control devices having a rotatable valve plug and a nonrotatable apertured valve disk biased toward one another for throttling gas flow through the disk to a burner.
The Sourdillon Arindex Co., of B.P. No. 10, Veigne, France 37250 has manufactured a linear flow valve sold as Model No. 831 for use with natural manufacture and mixed gaseous fuels to provide a linear turn down valve characteristic.